PostgreSQL provides a large
number of functions and operators for the built-in data types.
Users can also define their own functions and operators, as
described in Part V. The
psql commands \df and \do can be used
to show the list of all actually available functions and
operators, respectively.

If you are concerned about portability then take note that
most of the functions and operators described in this chapter,
with the exception of the most trivial arithmetic and comparison
operators and some explicitly marked functions, are not specified
by the SQL standard. Some of
the extended functionality is present in other SQL database management systems, and in many
cases this functionality is compatible and consistent between the
various implementations. This chapter is also not exhaustive;
additional functions appear in relevant sections of the
manual.